Hardenable cyanate compositions

ABSTRACT

A curable mixture which includes at least (a) 10 to 100 percent by weight, in relation to the sum of the components (a) and (b), of at least one bi- or polyfunctional aromatic cyanate or a prepolymer formed from at least one bi- or polyfunctional aromatic cyanate or a mixture formed from the abovementioned cyanates and/or prepolymers; (b) 0 to 90 percent by weight, in relation to the sum of the components (a) and (b), of at least one mono-, bi- or polyfunctional epoxy resin; (c) 0.5 to 30 percent by weight, in relation to the sum of the components (a) and (b), of at least one mono-, bi- or polyfunctional aromatic amine; and (d) 0 to 5 percent by weight, in relation to the sum of the components (a) and (b), of at least one catalyst from the group consisting of transition metal compounds and boron trihalides.

[0001] The invention relates to curable mixtures formed from aromaticcyanates or cyanate/epoxide mixtures, aromatic amines and optionallycatalysts for the preparation of polytriazine-based thermosettingmaterials. It additionally relates to the thermosetting substancesobtainable by curing these mixtures and to their use in the preparationof molded items.

[0002] The polytriazines obtainable from bi- or polyfunctional aromaticcyanates and the thermosetting materials obtainable from theabovementioned cyanates and epoxy resins are valuable materials becauseof their outstanding heat-resistance and good dielectric properties. Ineach case, the term polyfunctional cyanates, polyfunctional epoxides orpolyfunctional amines is understood to mean, here and subsequently,compounds comprising three or more cyanate, epoxy or amino groups in amolecule.

[0003] It is true that it is also possible to cure the abovementionedstarting materials by a purely thermal route but the curing is usuallycarried out by addition of catalytically effective transition metalcompounds, such as, for example, cobalt or copper acetylacetonate orzinc octanoate (“zinc octoate”). However, because of their toxicityand/or danger to the environment (in particular in the disposal ofmaterials prepared with them), and the possible influencing of theelectrical and magnetic properties, these are per se undesirable.

[0004] It was accordingly an object of the present invention to makeavailable alternative additives for the curing of aromatic cyanates andcyanate/epoxide mixtures which do not exhibit the abovementioneddisadvantages.

[0005] This object is achieved according to the invention by the curablemixtures as claimed in claim 1. It has been found, surprisingly, that,by the use of aromatic amines as curing agent of bi- or polyfunctionalcyanates or their mixtures with epoxides, not only can catalystscomprising heavy metals be dispensed with but also products withoutstanding properties are obtained after curing. Thus, the glasstransition temperature (T_(g)) in particular is markedly increased andthe cured products exhibit an improved impact strength. In addition, thethrough-curing is improved and the curing pattern, in particular thelatency in the curing, is improved.

[0006] The curable mixtures according to the invention comprise at leastthe following constituents:

[0007] (a) 10 to 100% by weight, in relation to the sum of thecomponents (a) and (b), of at least one bi- or polyfunctional aromaticcyanate or a prepolymer formed from at least one bi- or polyfunctionalaromatic cyanate or a mixture formed from the abovementioned cyanatesand/or prepolymers,

[0008] (b) 0 to 90% by weight, in relation to the sum of the components(a) and (b), of at least one mono-, bi- or polyfunctional epoxy resin,

[0009] (c) 0.5 to 30% by weight, in relation to the sum of thecomponents (a) and (b), of at least one mono-, bi- or polyfunctionalaromatic amine, and

[0010] (d) 0 to 5% by weight, in relation to the sum of the components(a) and (b), of at least one catalyst from the group consisting oftransition metal compounds and boron trihalides.

[0011] Transition metal compounds are to be understood as meaning bothsalts and coordination compounds, the transition metals in particularbeing able to be first row and second-row transition metals. Thisincludes, for example, coordination compounds, such as cobalt or copperacetylacetonate, or salts, such as zinc octanoate or zinc stearate.

[0012] Boron trihalides are in particular boron trifluoride and borontrichloride.

[0013] Use is preferably made, as bi- or polyfunctional aromaticcyanates, of those from the group consisting of the compounds of thegeneral formulae

[0014] in which R¹ is hydrogen, methyl or bromine and X is a divalentorganic radical chosen from the group consisting of —CH₂—, —CH(CH₃)—,—C(CH₃)₂—, —C(CF₃)₂—, —O—, —S—, —SO₂—, —C(═O)—, —OC(═O)—, —OC(═O)O— and

[0015] in which n is a number from 0 to 10 and R² is hydrogen or methyl;and

[0016] in which n has the abovementioned meaning. Mixtures of thesecompounds, prepolymers of these compounds, prepolymers formed frommixtures of these compounds and mixtures formed from prepolymers ofthese compounds can likewise also be used. Prepolymers are to beunderstood as the oligomers obtainable by partial trimerization. Thesecomprise both triazine groups produced by trimerization and unreactedcyanate groups. The cyanates are known compounds and are in many casesavailable commercially; likewise, the prepolymers are known and are insome cases available commercially or can be readily prepared from thecyanates.

[0017] Use is preferably made, as epoxy resins, of those from the groupconsisting of the compounds of the general formulae

[0018] in which R¹ and X have the abovementioned meanings, and thecorresponding oligomers;

[0019] in which n and R² have the abovementioned meanings: and

[0020] in which n has the abovementioned meaning. These compounds arealso known and are available commercially from various manufacturers.

[0021] Use is preferably made, as aromatic amines, of those from thegroup consisting of the compounds of the general formulae

[0022] in which R³, R⁴ and R⁵ are, independently of one another,hydrogen, C₁₋₄-alkyl or halogen, and

[0023] in which R⁶, R⁷ and R⁸ are, independently of one another,hydrogen or C₁₋₄-alkyl. These compounds are also known and are in manycases available commercially. Compounds of the formula VII are, forexample, used as chain extenders in polyurethanes and those of theeformula VIII as amine component in polyureas or as starting materialsfor the preparation of isocyanates.

[0024] The polytriazine-based thermosetting substances obtainable bythermal curing of the mixtures described above, optionally with additionof fillers and/or auxiliaries, are likewise a subject matter of theinvention. Fillers and auxiliaries are to be understood as in particularreinforcing materials in the form of fabrics, fibers or particles,colorants or other additives for obtaining particular mechanical,optical, electrical or magnetic properties or for improving theprocessing characteristics. These fillers and auxiliaries are known to aperson skilled in the art.

[0025] The use of the thermosetting substances thus obtainable in thepreparation of molded items for electronic equipment, aircraft,spacecraft, road vehicles, rail vehicles, watercraft and industrialpurposes is an additional subject matter of the invention.

[0026] The following exemplary embodiments clarify the invention withouta limitation to be seen therein.

EXAMPLES 1-8

[0027] Mixtures of cyanates (Primaset® PT 15 from Lonza AG; formula II,R²=H, viscosity 20-30 Pa·s at 80° C.), optionally epoxide (Dow DER 330;formula IV, R¹=H, X=—C(CH₃)₂—), and amine (Lonzacure® DETDA from LonzaAG, formula VIII, R⁶=R⁷=Et, R⁸=Me, mixture of isomers) were prepared andthermally cured. The glass transition temperature (T_(g)) was determinedfrom the cured test specimens by thermomechanical analysis. The mixingproportions, curing conditions and glass transition temperatures aresummarized in the following table 1. TABLE 1 Epoxide Cyanate Amine Curetemperature Cure time Example No. [g] [g] [g] T_(g) [° C.] [° C. ] [min]1 — 100 1.0 361 150 60 2 — 100 2.5  361¹⁾ 150 60 3 — 100 5.0 368 150 604 — 100 10.0 377 150 60 5 75 25 2.5 375 150 60 6 75 25 5.0 367 150 60 775 25 10.0 351 150 60 8 75 25 10.0 378 150/200/250 180/180/180

EXAMPLES 9-12

[0028] Processing was carried out as described in the above examples butusing Lonzacure® M-CDEA (formula VII, R³=R⁴=Et, R⁵=Cl) as amine. Theresults are summarized in the following table 2. TABLE 2 Epoxide CyanateAmine Cure temperature Cure time Example No. [g] [g] [g] T_(g) [° C.] [°C.] [min] 9 — 100 5.0  384¹⁾ 150 60 10 75 25 2.5 366 150/200/250180/180/180 11 75 25 5.0 362 150 60 12 75 25 10.0 370 150 60

EXAMPLES 13-16

[0029] Precessing was carried out as described in examples 9-12 butusing the cyanate Primaset® CT 90 (formula II, R²=Me, softeningpoint >60° C.) instead of the cyanate Primaset® PT 15. The results aresummarized in the following table 3. TABLE 3 Epoxide Cyanate Amine Curetemperature Cure time Example No. [g] [g] [g] T_(g) [° C.] [° C.] [min]13 75 25 5.0  369¹⁾ 150 60 14 75 25 5.0 376 150/200/250 180/180/180 1575 25 10.0 372 150 60 16 75 25 10.0 373 150/200/250 180/180/180

1. A curable mixture, at least comprising (a) 10 to 100% by weight, inrelation to the sum of the components (a) and (b), of at least one bi-or polyfunctional aromatic cyanate or a prepolymer formed from at leastone bi- or polyfunctional aromatic cyanate or a mixture formed from theabovementioned cyanates and/or prepolymers, (b) 0 to 90% by weight, inrelation to the sum of the components (a) and (b), of at least onemono-, bi- or polyfunctional epoxy resin, (c) 0.5 to 30% by weight, inrelation to the sum of the components (a) and (b), of at least onemono-, bi- or polyfunctional aromatic amine, and (d) 0 to 5% by weight,in relation to the sum of the components (a) and (b), of at least onecatalyst from the group consisting of transition metal compounds andboron trihalides.
 2. The curable mixture as claimed in claim 1,characterized in that the bi- or polyfunctional aromatic cyanate ischosen from the group consisting of the compounds of the generalformulae

in which R¹ is hydrogen, methyl or bromine and X is chosen from thegroup consisting of —CH₂—, —CH(CH₃)—, —C(CH₃)₂—, —C(CF₃)₂—, —O—, —S—,—SO₂—, —C(═O)—, —OC(═O)—, —OC(═O)O— and

in which n is a number from 0 to 10 and R² is hydrogen or methyl; and

in which n has the abovementioned meaning, and prepolymers formed fromone or more of these compounds.
 3. The curable mixture as claimed inclaim 1, characterized in that the epoxy resin is chosen from the groupconsisting of the compounds of the general formulae

in which R¹ and X have the meanings mentioned in claim 2, and thecorresponding oligomers,

in which n and R² have the meanings mentioned in claim 2, and

in which n has the abovementioned meaning.
 4. The curable mixture asclaimed in claim 1, characterized in that the aromatic amine is chosenfrom the group consisting of the compounds of the general formulae

in which R³, R⁴ and R⁵ are, independently of one another, hydrogen,C₁₋₄-alkyl or halogen, and

in which R⁶, R⁷ and R⁸ are, independently of one another, hydrogen orC₁₋₄-alkyl.
 5. A polytriazine-based thermosetting substance, obtainableby thermal curing of the mixture as claimed in claim 1, optionally withaddition of fillers and/or auxiliaries.
 6. The use of the thermosettingsubstance as claimed in claim 5 in the preparation of molded items forelectronic equipment, aircraft, spacecraft, road vehicles, railvehicles, watercraft and industrial purposes.
 7. The curable mixture asclaimed in claim 2, characterized in that the epoxy resin is chosen fromthe group consisting of the compounds of the general formulae

in which R¹ and X have the meanings mentioned in claim 2, and thecorresponding oligomers,

in which n and R² have the meanings mentioned in claim 2, and

in which n has the abovementioned meaning.
 8. The curable mixture asclaimed in claim 2, characterized in that the aromatic amine is chosenfrom the group consisting of the compounds of the general formulae

in which R³, R⁴ and R⁵ are, independently of one another, hydrogen,C₁₋₄-alkyl or halogen, and

in which R⁶, R⁷ and R⁸ are, independently of one another, hydrogen orC₁₋₄-alkyl.
 9. The curable mixture as claimed in claim 3, characterizedin that the aromatic amine is chosen from the group consisting of thecompounds of the general formulae

in which R³, R⁴ and R⁵ are, independently of one another, hydrogen,C₁₋₄-alkyl or halogen, and

in which R⁶, R⁷ and R⁸ are, independently of one another, hydrogen orC₁₋₄-alkyl.
 10. A polytriazine-based thermosetting substance, obtainableby thermal curing of the mixture as claimed in claim 2, optionally withaddition of fillers and/or auxiliaries.
 11. A polytriazine-basedthermosetting substance, obtainable by thermal curing of the mixture asclaimed in claim 3, optionally with addition of fillers and/orauxiliaries.
 12. A polytriazine-based thermosetting substance,obtainable by thermal curing of the mixture as claimed in claim 4,optionally with addition of fillers and/or auxiliaries.
 13. The use ofthe thermosetting substance as claimed in claim 10 in the preparation ofmolded items for electronic equipment, aircraft, spacecraft, roadvehicles, rail vehicles, watercraft and industrial purposes.
 14. The useof the thermosetting substance as claimed in claim 11 in the preparationof molded items for electronic equipment, aircraft, spacecraft, roadvehicles, rail vehicles, watercraft and industrial purposes.
 15. The useof the thermosetting substance as claimed in claim 12 in the preparationof molded items for electronic equipment, aircraft, spacecraft, roadvehicles, rail vehicles, watercraft and industrial purposes.